The replacement of
halogen-free flame retardants, driven by health
concerns, has sparked a large demand for new “green”
flame-retardant alternatives. Inspired by the natural flame-retardant
properties of Cladophora sp. algae coated with silica
diatoms, a silica sol–gel method has been employed to improve
the fire resistance of common, open-cell polyurethane (PU) foams.
The Stöber process with components 2-propanol, water, tetraethyl
orthosilicate (TEOS), and ammonium hydroxide was employed for silica
nanoparticle synthesis on the inside walls and struts of PU foam.
Upon ignition, the treated foams briefly burn, followed by formation
of a propagating char front that leads to self-extinguishment. Most
importantly, the coating of silica nanoparticles prevents dripping
of flaming residues seen in common untreated PU foams. Microcomputerized
tomography of silica-treated foam after burning reveals that char
formation is confined to the outer edges of the bulk foam. Via cone
calorimetry, the peak heat release rate of a 0.5 M TEOS foam was reported
as dropping from 560 to 262 kW/m2, relative to untreated
foam. These results, coupled with the ease of application of the silica
coatings, suggest a viable and scalable approach to the mitigation
of burning of common open-cell PU foams.
Poly(acrylic acid) gels synthesized via free-radical polymerization of acrylic acid and high molarities of salt show properties quite different from such gels synthesized without salt. Enhanced properties include increased extensibility and modulus.
This manuscript is dedicated to Professor Mitsuo Sawamoto's outstanding achievements in polymer chemistry and recognizes his recent retirement from 40 years of exceptional service to Kyoto University. ABSTRACT: Self-assembly of amphiphilic ABA random triblock copolymers in water serves as a novel approach to create unique structure micelles connected with flexible linkages. The ABA triblock copolymers consist of amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) and hydrophobic dodecyl pendants as the A segments and a hydrophilic poly(ethylene oxide) (PEO) as the middle B segment. The A block is varied in dodecyl methacrylate content of 20%-50% and degree of polymerization (DP) of 100-200. By controlling the composition and DP of the A block, various architectures can be tailor-made as micelles in water: PEO-linked double core unimer micelles, PEOlooped unimer or dimer micelles, and multichain micelles. Those PEO-linked or looped micelles further exhibit thermoresponsive solubility in water.
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